Calculations of the charge distribution in dodecyltrimethylammonium: a quantum chemical investigation.

In this work we report the atomic partial charges evaluated on dodecyltrimethylammonium ion. The values obtained from 17 quantum methods [CHELP, CHELPG, MK, NPA at (HF, LDA, PBE, B3LYP)//6-31G++(d,p) level and APT at B3LYP//6-31G++(d,p)] on the molecule optimised at B3LYP/6-31G++(d,p) level were compared to two semiempirical methods (Gasteiger and Qeq) and the commercial force field PCFF. All methods based on quantum calculation gave a positive charge delocalised on at least the first four alkyl groups of the tail.